[PATCH 4/5] Add fair-user scheduler

Srivatsa Vaddagiri
2007-09-24T16:45:01Z

Enable user-id based fair group scheduling. This is usefull for anyone
who wants to test the group scheduler w/o having to enable
CONFIG_CGROUPS.

A separate scheduling group (i.e struct task_grp) is automatically created for
every new user added to the system. Upon uid change for a task, it is made to
move to the corresponding scheduling group.

A /proc tunable (/proc/root_user_share) is also provided to tune root
user's quota of cpu bandwidth.

Signed-off-by : Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by : Dhaval Giani <dhaval@linux.vnet.ibm.com>

---
include/linux/sched.h | 4 +++
init/Kconfig | 13 ++++++++++++
kernel/sched.c | 9 ++++++++
kernel/sched_debug.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++
kernel/user.c | 43 +++++++++++++++++++++++++++++++++++++++++
5 files changed, 121 insertions(+)

Index: linux-2.6.23-rc6/include/linux/sched.h
===================================================================
--- linux-2.6.23-rc6.orig/include/linux/sched.h
+++ linux-2.6.23-rc6/include/linux/sched.h
@@ -596,6 +596,10 @@ struct user_struct {
/* Hash table maintenance information */
struct hlist_node uidhash_node;
uid_t uid;
+
+#ifdef CONFIG_FAIR_USER_SCHED
+ struct task_grp *tg;
+#endif
};

extern struct user_struct *find_user(uid_t);
Index: linux-2.6.23-rc6/init/Kconfig
===================================================================
--- linux-2.6.23-rc6.orig/init/Kconfig
+++ linux-2.6.23-rc6/init/Kconfig
@@ -289,6 +289,19 @@ config FAIR_GROUP_SCHED
This feature lets cpu scheduler recognize task groups and control cpu
bandwidth allocation to such task groups.

+choice
+ depends on FAIR_GROUP_SCHED
+ prompt "Basis for grouping tasks"
+ default FAIR_USER_SCHED
+
+ config FAIR_USER_SCHED
+ bool "user id"
+ help
+ This option will choose userid as the basis for grouping
+ tasks, thus providing equal cpu bandwidth to each user.
+
+endchoice
+
config SYSFS_DEPRECATED
bool "Create deprecated sysfs files"
default y
Index: linux-2.6.23-rc6/kernel/sched.c
===================================================================
--- linux-2.6.23-rc6.orig/kernel/sched.c
+++ linux-2.6.23-rc6/kernel/sched.c
@@ -199,7 +199,12 @@ struct task_grp init_task_grp = {
.cfs_rq = init_cfs_rq_p,
};

+#ifdef CONFIG_FAIR_USER_SCHED
+#define INIT_TASK_GRP_LOAD 2*NICE_0_LOAD
+#else
#define INIT_TASK_GRP_LOAD NICE_0_LOAD
+#endif
+
static int init_task_grp_load = INIT_TASK_GRP_LOAD;

/* return group to which a task belongs */
@@ -207,7 +212,11 @@ static inline struct task_grp *task_grp(
{
struct task_grp *tg;

+#ifdef CONFIG_FAIR_USER_SCHED
+ tg = p->user->tg;
+#else
tg = &init_task_grp;
+#endif

return tg;
}
Index: linux-2.6.23-rc6/kernel/sched_debug.c
===================================================================
--- linux-2.6.23-rc6.orig/kernel/sched_debug.c
+++ linux-2.6.23-rc6/kernel/sched_debug.c
@@ -214,6 +214,49 @@ static void sysrq_sched_debug_show(void)
sched_debug_show(NULL, NULL);
}

+#ifdef CONFIG_FAIR_USER_SCHED
+
+static DEFINE_MUTEX(root_user_share_mutex);
+
+static int
+root_user_share_read_proc(char *page, char **start, off_t off, int count,
+ int *eof, void *data)
+{
+ int len;
+
+ len = sprintf(page, "%d\n", init_task_grp_load);
+
+ return len;
+}
+
+static int
+root_user_share_write_proc(struct file *file, const char __user *buffer,
+ unsigned long count, void *data)
+{
+ unsigned long shares;
+ char kbuf[sizeof(unsigned long)+1];
+ int rc = 0;
+
+ if (copy_from_user(kbuf, buffer, sizeof(kbuf)))
+ return -EFAULT;
+
+ shares = simple_strtoul(kbuf, NULL, 0);
+
+ if (!shares)
+ shares = NICE_0_LOAD;
+
+ mutex_lock(&root_user_share_mutex);
+
+ init_task_grp_load = shares;
+ rc = sched_group_set_shares(&init_task_grp, shares);
+
+ mutex_unlock(&root_user_share_mutex);
+
+ return (rc < 0 ? rc : count);
+}
+
+#endif /* CONFIG_FAIR_USER_SCHED */
+
static int sched_debug_open(struct inode *inode, struct file *filp)
{
return single_open(filp, sched_debug_show, NULL);
@@ -236,6 +279,15 @@ static int __init init_sched_debug_procf

pe->proc_fops = &sched_debug_fops;

+#ifdef CONFIG_FAIR_USER_SCHED
+ pe = create_proc_entry("root_user_share", 0644, NULL);
+ if (!pe)
+ return -ENOMEM;
+
+ pe->read_proc = root_user_share_read_proc;
+ pe->write_proc = root_user_share_write_proc;
+#endif
+
return 0;
}

Index: linux-2.6.23-rc6/kernel/user.c
===================================================================
--- linux-2.6.23-rc6.orig/kernel/user.c
+++ linux-2.6.23-rc6/kernel/user.c
@@ -50,8 +50,41 @@ struct user_struct root_user = {
.uid_keyring = &root_user_keyring,
.session_keyring = &root_session_keyring,
#endif
+#ifdef CONFIG_FAIR_USER_SCHED
+ .tg = &init_task_grp,
+#endif
};

+#ifdef CONFIG_FAIR_USER_SCHED
+static void sched_destroy_user(struct user_struct *up)
+{
+ sched_destroy_group(up->tg);
+}
+
+static int sched_create_user(struct user_struct *up)
+{
+ int rc = 0;
+
+ up->tg = sched_create_group();
+ if (IS_ERR(up->tg))
+ rc = -ENOMEM;
+
+ return rc;
+}
+
+static void sched_switch_user(struct task_struct *p)
+{
+ sched_move_task(p);
+}
+
+#else /* CONFIG_FAIR_USER_SCHED */
+
+static void sched_destroy_user(struct user_struct *up) { }
+static int sched_create_user(struct user_struct *up) { return 0; }
+static void sched_switch_user(struct task_struct *p) { }
+
+#endif /* CONFIG_FAIR_USER_SCHED */
+
/*
* These routines must be called with the uidhash spinlock held!
*/
@@ -109,6 +142,7 @@ void free_uid(struct user_struct *up)
if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
uid_hash_remove(up);
spin_unlock_irqrestore(&uidhash_lock, flags);
+ sched_destroy_user(up);
key_put(up->uid_keyring);
key_put(up->session_keyring);
kmem_cache_free(uid_cachep, up);
@@ -150,6 +184,13 @@ struct user_struct * alloc_uid(struct us
return NULL;
}

+ if (sched_create_user(new) < 0) {
+ key_put(new->uid_keyring);
+ key_put(new->session_keyring);
+ kmem_cache_free(uid_cachep, new);
+ return NULL;
+ }
+
/*
* Before adding this, check whether we raced
* on adding the same user already..
@@ -157,6 +198,7 @@ struct user_struct * alloc_uid(struct us
spin_lock_irq(&uidhash_lock);
up = uid_hash_find(uid, hashent);
if (up) {
+ sched_destroy_user(new);
key_put(new->uid_keyring);
key_put(new->session_keyring);
kmem_cache_free(uid_cachep, new);
@@ -184,6 +226,7 @@ void switch_uid(struct user_struct *new_
atomic_dec(&old_user->processes);
switch_uid_keyring(new_user);
current->user = new_user;
+ sched_switch_user(current);

/*
* We need to synchronize with __sigqueue_alloc()

--
Regards,
vatsa